A nostril (or naris , plural ''nares'' ) is one of the two channels of the nose
, from the point where they bifurcate to the external opening. In bird
s and mammal
s, they contain branched bones or cartilages called turbinate
s, whose function is to warm air on inhalation and remove moisture on exhalation. Fish
do not breathe through their noses, but they do have two small holes used for smelling
, which can also be referred to as nostrils.
s, the nasal cycle
is the normal ultradian cycle
of each nostril's blood vessels becoming engorged in swelling, then shrinking.
The nostrils are separated by the septum
. The septum can sometimes be deviated
, causing one nostril to appear larger than the other. With extreme damage to the septum and columella, the two nostrils are no longer separated and form a single larger external opening.
Like other tetrapod
s, humans have two external nostrils (anterior nares) and two additional nostrils at the back of the nasal cavity, inside the head (posterior nares, posterior nasal apertures or choana
e). They also connect the nose to the throat (the nasopharynx), aiding in respiration. Though all four nostrils were on the outside the head of our fish ancestors, the nostrils for outgoing water (excurrent nostrils) migrated to the inside of the mouth, as evidenced by the discovery of ''Kenichthys campbelli
'', a 395-million-year-old fossilized fish which shows this migration in progress. It has two nostrils between its front teeth, similar to human embryo
s at an early stage. If these fail to join up, the result is a cleft palate
Each external nostril contains approximately 1000 strands of nasal hair
It is possible for humans to smell different olfactory
inputs in the two nostrils and experience a perceptual rivalry akin to that of binocular rivalry
when there are two different inputs to the two eyes.
are distinguished from other birds by having tubular extensions of their nostrils.
* Dilator naris muscle
* Variant singular form ''nare
* Nasal cycle